This application relates to post processing of laser peened articles.
Laser peening is a surface treatment that induces deep compressive residual stresses. The compression increases the damage tolerance of a metal material. One method of laser peening an article is to prepare the material by covering it with a sacrificial ablative layer. Typically, this ablative layer is an applied medium, such as tape or paint to avoid base metal damage of the component during laser peening.
A medium, typically water, covers the ablative layer and acts to confine the plasma that will develop after the laser strike. A laser pulse is directed at the material. When the laser hits the material, an explosion of expanding plasma is formed between the ablative layer and the water layer. This explosion of plasma creates a shock wave that compresses and works the outer layer of the material.
Another method of laser peening a material is to use the surface of the base metal itself as an ablative medium. A portion of the base material is used to create the plasma that produces the shock wave, subsequently damaging the base material surface. An example of such damage is micro-cracking, as well as detrimental tensile residual stress. This damaged material is known as a remelt layer.
Post processing to remove the remelt layer and finish the component surface has been proposed.